The Golden Years

Keo (foreground) and June stand in front of the ice “cake” provided for Keo’s 50th birthday celebration. This milestone highlighted the care provided to Keo and other geriatric animals throughout Lincoln Park Zoo.

Geriatric Animals Thrive Within Lincoln Park Zoo's Culture of Care

The crowd gathered outside Regenstein Center for African Apes had come to Lincoln Park Zoo in late June to witness a milestone. Chimpanzee Keo, one of the zoo’s most-beloved animals, was turning 50.

A celebration had been announced, and adult visitors, summer campers and kids were arrayed around the outdoor exhibit, waiting excitedly for a peek at the ape of the hour. News cameras gathered at the glass wall to record the event. Keepers laughed among themselves, sharing Keo stories passed down during the chimpanzees’ 49 years at the zoo. Everyone ogled the centerpiece of the celebration, a 600-pound ice “cake.” Donated by Nadeau’s Ice Sculpture Inc., it was composed of three frozen tiers stuffed with fresh fruits and berries. Topped with a hand-carved “50,” the “cake” had softened just enough after an hour in the sun for probing chimpanzee fingers to begin to find fruit.

When the doors opened, Keo electrified the crowd by dashing back and forth along the wall of his exhibit. Photographers snapped pictures. A hand-drawn birthday banner was unfurled. And the “cake” was studiously ignored by Keo, leaving the females in his group—June, Vicky and Kibali—to eagerly dig into the cool ice and frozen treats, eventually dragging the “50” to a shady nook where it could be consumed at leisure.

Why such a big deal? The half-century mark reflected Keo’s status as the oldest living male chimpanzee in any zoo, a record shared with Cobby, a male chimpanzee at San Francisco Zoo. Beyond that, though, Keo’s 50th birthday reflected a zoo success. In the celebration, you could see the decades of care, check-ups and, sure, good genes that helped him attain his old age.

These kinds of milestones have become almost commonplace at Lincoln Park Zoo. True, no other animals have received 600-pound blocks of ice. Most aren’t likely to make it to 50 either. After all, life expectancies vary widely among species; an Amur tiger is elderly at 15 while dwarf crocodile R1 is still going strong at 68.

But more animals are living longer than ever before, thanks to regular check-ups, scientifically designed diets and top-notch care by keepers and veterinary staff. Aging can bring challenges. But it can bring wonderful rewards as well, namely the prospect of animals aging gracefully into their golden years, engaging visitors with another stage of the animal life cycle, one that would be unknown in the harshness of the wild.

Committed to Care
As animals age, many of them begin to experience the same afflictions that affect older people. Aches and pains set in; joints develop arthritis. Heart disease becomes a concern, as do bumps and lumps that have the potential of developing into something more serious.

These problems receive the attention of Lincoln Park Zoo’s veterinary staff, who display special diligence in monitoring the well-being of the zoo’s geriatric animals. All animals throughout the zoo receive routine physicals where their weight is monitored, their vital signs checked and body images and blood tests preventively probe for health issues.

Beyond regular check-ups, much of the veterinarians’ work with geriatric animals is rooted in day-to-day consultations with zookeepers on subtle shifts in an animal’s behavior—a leg that’s being favored or signs of a loss of appetite. “We work closely with keepers, educating them on how to report observations for the animals in their care,” says Kathryn Gamble, D.V.M., director of Veterinary Services.

Keo’s group is one of many that benefits from this comprehensive care, with the male being joined in his geriatric status by June (42) and Vicky (44). All of the apes are in good shape—they move actively around their exhibit and have little trouble climbing to the treetops. Cardiologists from local hospitals perform cardiac ultrasounds during regular exams to confirm the health of the chimpanzees’ hearts. Regular medication also helps to manage heart disease. (Much like people, chimpanzees are vulnerable to cardiac problems as they age.)

Beyond medical interventions, keepers have instituted a number of changes to help the chimpanzees age gracefully. Those trips to the treetops the chimpanzees embark on? They’re aided by extra ropes strung throughout the exhibit to provide easier handholds for aging arms. Concerns about aching joints? They’re alleviated by the building’s mulch substrate, installed to provide additional cushioning for well-traveled knees.

Beyond altering exhibits to accommodate animals, keepers also conduct daily conditioning sessions to encourage animals to contribute to their own care. By using positive reinforcement to spur desired behaviors, keepers have prepped chimpanzees to present arms, legs, fingers and toes for inspection. They’ve trained them to step onto scales for weight monitoring or present themselves for an injection of medicine. They’re even working on tooth-brushing sessions to help promote dental health. “These one-on-one sessions give us a great chance to see how they’re doing,” says RCAA Lead Keeper Dominic Calderisi. “We check out their alertness, how they’re moving, how they react to social situations. As soon as anything comes up, we’re on the phone with the vets, and they’ll come over and look at it.”

Adapting to Age
Similar scenarios are in place throughout the zoo to ensure the comfort and health of geriatric animals. At the Kovler Lion House, ramps, logs and lower ledges help the building’s resident servals (19 and 17) and Afghan leopard (19) navigate to the heights of their exhibit, an important concession for these climbing mammals. Extra ropes and vines help the geriatric bat colony at Regenstein Small Mammal-Reptile House reach the heights of their habitat when they don’t feel like flapping their wings. The 15-year-old Grant’s gazelle at Regenstein African Journey enjoys the extra warmth of a heat lamp in her stall in winter. And the adult black bears (21) at the Pritzker Family Children’s Zoo receive regular medication to help them cope with their aching joints.

Arthritis is one of the biggest concerns for aging mammals. “Because we do such a good job with the animals in our care, they live a lot longer, and structurally their skeletons gradually fail,” explains Gamble. As arthritis and related afflictions have become more common, treatments have advanced as well. Exhibit adjustments, anti-inflammatories and nutritional supplements are common treatments to increase comfort. “Many of our animals receive nutriceuticals—supplements that help joints produce lubricating proteins to maintain normal joint function. When I started practicing 20 years ago, nobody used them. Now they’re one of the bigger components of our arthritis budget. That’s just one example of how the care has evolved.”

Slowing Down
While the majority of geriatric animals reside in their exhibits with modifications and changes in care, some find it in their best interest to live behind the scenes as needs evolve. At Regenstein Small Mammal-Reptile House, the resident Asian small-clawed otter pair (16) was moved to an interior exhibit after the male developed knee issues making it difficult for him to navigate his exhibit in the building’s Ecosystem Area. “He had to go up and down a ramp to get to his exhibit, but now he has a nice, level surface with a big pool and lots of enrichment and exercise,” says Curator Diane Mulkerin.

Down the hall, an elderly golden-headed lion tamarin occupies another sizable indoor exhibit. This 18-year-old monkey has severe liver disease, but a drug regimen maintains his health. At the same time, regular enrichment—boxes to climb in, mealworms to dig out of dirt basins, scented branches for him to sniff—keeps him active. “He loves watching everything that goes on around him—including us,” says Keeper Dan Mondl. “He’s really curious.”

Like all geriatric animals, the tamarin has quality-of-life parameters in place, guidelines developed by veterinary staff and zookeepers to ensure that animals continue to benefit from the care provided. Quality-of-life plans keep the emotional aspect of caring for animals—the daily interactions, the deep connection that’s formed during years of care—from interfering with what’s best for them.

“No matter how good the care is, animals will continue to age,” says Gamble. “But these animals would have no chance of living this long in the wild, where disease, predators and finding food are all daily obstacles. Here, we provide care, and the main focus is on enhancing their quality of life. That’s always the ultimate goal.”